Scientific name: Satyrium w-album

A small butterfly which lives in the tops of elm trees throughout England and Wales but is often overlooked.

Underwings brown with white W-shaped streak, an orange edge and small tails. Black Hairstreak is similar but has row of black spots on hindwing. The White-letter Hairstreak has the erratic, spiralling flight typical of Hairstreaks.

Difficult to spot as it flies around the tops of trees, particularly Elms. It occasionally comes down to ground level to nectar on flowers, especially privet and bramble.

The species declined in the 1970s when its foodplants were reduced by Dutch Elm disease but it is recovering in a few areas.

Size and Family

Family: Hairstreaks

Size: Small/Medium

Wing Span Range (male to female): 36mm

Conservation Status

Butterfly Conservation priority: High

Section 41 species of principal importance under the 2006 NERC Act in England

Section 41 species of principal importance under the 2006 NERC Act in Wales

Caterpillar Foodplants

The butterfly breeds on various elm species, including Wych Elm (Ulmus glabra), English Elm (U. procera) and Small-leaved Elm (U. minor). Research at one site has indicated a preference for (and a higher success rate on) Wych Elm. It breeds on mature trees or abundant sucker growth near dead trees. It has also been shown to survive on the Dutch Elm Disease-resistant variety of U. japonica, Sapporo Autumn Gold.

Habitat

The butterfly breeds where elms occur in sheltered hedgerows, mixed scrub and on the edges of woodland rides. The butterfly can also be found on large isolated elms.